JP2009066854A - Thermal print head and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal print head and a method for manufacturing the same in which, in the operation of the thermal print head, high speed and high definition thereof can be easily obtained. <P>SOLUTION: A resistor substrate part 12A and a driving circuit substrate part 12B are formed on a radiation substrate 11; a plurality of separated insulation layers 14 comprising an insulator material separated in an island form are formed on the surface of a supporting substrate 13; and a heating resistor layer 15 covering them is formed. A gap G is formed on the heating resistor layer 15 on the separated insulation layer 14 to form a first electrode 16a and a second electrode 16b, and the gap G portion is used as an exothermic part 17. Then, an overcoat 18 which covers at least the exothermic part 17 is formed. Thus, each exothermic part 17 is formed on one separated insulation layer 14. In addition, a drive IC20 on a driving circuit substrate 19 is electrically connected to the above electrodes by a bonding wire W, and a sealer 21 hermetically seals them. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a thermal print head for recording on a recording medium by a thermal method or a thermal transfer method, and more particularly to a thermal print head that facilitates high-speed operation and high image quality, and a manufacturing method thereof.

  The thermal print head is an output device that forms an image made up of characters on a recording medium such as a thermal recording paper or a thermal transfer ink ribbon by utilizing the heat generated by the heat generating portion. It is widely used in recording devices such as barcode printers, weighing machines, digital plate-making machines, video printers, imagers, and seal printers. Generally, a thermal print head has a structure in which a resistor substrate portion provided with a heat generating portion for image formation and a drive circuit substrate portion mounted with a drive IC are arranged on one main surface of a heat dissipation substrate. Yes.

  Here, a conventional thermal print head will be described with reference to FIGS. FIG. 5 is a partially cut-out top view with a part thereof extracted, and FIG. 6 is a cross-sectional view in the direction (sub-scanning direction) in which the segment ZZ in FIG. The thermal print head extends to a required length along a direction (main scanning direction) orthogonal to the sub-scanning direction.

  As shown in FIGS. 5 and 6, in the thermal print head 100, for example, a resistor substrate portion 102 </ b> A and a drive circuit substrate portion 102 </ b> B are provided adjacent to each other on the main surface of the heat dissipation substrate 101. In the resistor substrate portion 102A, the support substrate 103 is adhered on the main surface of the heat dissipation substrate 101, and the glaze layer 104 extends on the support substrate 103 in the main scanning direction of the head as shown in FIG. It is provided integrally. The glaze layer 104 is formed by a thick film technique based on coating formation by screen printing and firing.

  Then, the heating resistor layer 105 is formed so as to cover the surface of the glaze layer 104 and the surface of the support substrate 103 as described above, and the first electrode 106a and the second electrode 106b are spaced on the heating resistor layer 105. They are arranged facing each other across G. Here, the pair of electrodes 106 composed of the first electrode 106a and the second electrode 106b are electrically connected to the heating resistor layer 105 so as to overlap with each other, and the heating resistor layer 105 exposed in the gap G is used as the heating part. 107.

  As shown in the figure, the pair of electrodes 106 serving as energization electrodes of the heat generating portion 107 and the heat generating portion 107 form one heat generating element, and in the main scanning direction of the thermal print head 100, for example, an element density of 10 / mm. The heating element arrays are arranged in a row. Further, the edge portion of the first electrode 106a is exposed and entirely covered with a protective film 108 for bonding wire connection described later.

  On the other hand, the drive circuit board portion 102B includes a drive circuit board 109 and the like attached to the heat dissipation board 101, a circuit pattern (not shown) and the like are formed on the surface of the board, and a drive IC 110 and the like are mounted. A bonding wire W is used to electrically connect the energizing electrode of the resistor substrate portion 102A and the drive IC 110 of the drive circuit substrate portion 102B and between the drive IC 110 and the circuit pattern of the drive circuit substrate portion 102B. It is connected. These bonding wires W and the driving IC 110 are hermetically sealed by a sealing material 111 made of, for example, an epoxy resin.

  In image formation on a recording medium using the thermal print head 100, a thermal recording paper, a thermal transfer ink ribbon, or the like (not shown) is sandwiched between the protective film 108 on the heat generating portion 107 area and a so-called platen roller. And conveyed at a predetermined speed in the sub-scanning direction. In this conveyance, for example, the heat-sensitive recording medium is heated by the heat generating unit 107, and the recording medium is printed by the heat.

  As shown in FIG. 6, such a thermal print head 100 has a structure of a glaze layer 104 raised in a convex shape, thereby improving the adhesion of a recording medium or the like to the heat generating portion 107 and storing heat of the heat generating portion 107. Therefore, it is possible to easily reduce the power consumption. In addition, the size of the support substrate 103 in the sub-scanning direction can be easily reduced.

A thermal print head having the above-described configuration is described in Patent Document 1 and the like.
JP 2001-301217 A

  However, the thermal print head 100 as described above has limitations in speeding up and high image quality in its operation. This is because, as described above, the thick film glaze layer 104 extending in the main scanning direction of the head and integrally formed has a limit of a few tens of μm even if it is thin. This is because heat history control in the next printing or printing of neighboring heating elements becomes more complicated, and the higher the density of the elements, the more difficult it is to shorten the non-printing time due to the heat radiation of the glaze layer 104.

  Usually, in the operation of the thermal print head, there are printing time and non-printing time on the recording medium. In order to increase the speed of the head operation, it is essential to shorten the non-printing time as well as the printing time. Here, when printing is performed by one heating element, the temperature of the surrounding glaze layer 104 rises due to heat generation, and heat storage occurs. Since the glaze layer 104 is a heat insulating layer, if the heat radiation is not sufficient in the next printing performed after the printing of one heating element or the printing of another heating element adjacent thereto, the printing point is cut off. As a result, the image quality blur in the sub-scanning direction becomes obvious and is visually recognized. For this reason, it is essential to secure an appropriate non-printing time for guaranteeing heat dissipation as thermal history control of the glaze layer 104, especially for printing of adjacent heating elements, and shortening the non-printing time. Be restricted.

  Thus, the conventional thermal print head 100 has a structure in which it is difficult to achieve high speed and high image quality.

  The present invention has been made in view of the above-described circumstances, and a thermal print head in which the non-printing time for thermal history control is reduced in the operation of the thermal print head and its high speed and high image quality can be easily achieved. An object is to provide a manufacturing method.

  In order to achieve the above object, a thermal print head according to the present invention comprises a support substrate, a plurality of heat insulation layers made of an insulating material formed on the surface of the support substrate in an island shape, and the heat insulation layer. A heating resistor layer formed on the surface of the supporting substrate, a heating element group formed by arranging a plurality of electrodes formed with a gap on the heating resistor layer, and the electrode exposed in the gap portion of the electrode The heating resistor layer is used as a heat generating portion of the heat generating element, and includes a protective film that covers at least the heat generating portion and is laminated on the heat insulating layer and the support substrate, and the heat generating portions are separated from each other. The structure is formed on one heat insulating layer.

  And the manufacturing method of the thermal print head concerning this invention forms the some heat insulation layer which formed the process of forming an insulator thin film in one main surface of a support substrate, and etched the said insulator thin film into the island shape A step of stacking and depositing a heating resistor layer and an electrode film covering the heat retaining layer and the support substrate, and processing the heating resistor layer and the electrode film into a required pattern, respectively. Forming a plurality of heat generating elements having heat generating parts, and forming the heat generating parts of each heat generating element on the separated one heat insulating layer; covering at least the heat generating parts; and on the heat insulating layer and the support And a step of forming a protective film to be laminated on the substrate.

  According to the configuration of the present invention, it is possible to provide a thermal print head that can reduce the non-printing time for thermal history control in the operation of the thermal print head, and that can easily increase the speed and improve the image quality, and the manufacturing method thereof.

  An embodiment of the present invention will be described with reference to FIG. 1, FIG. 2, and FIG. Here, FIG. 1 is a partially cut-out top view of a part of the thermal print head extracted. 2 and 3 are cross-sectional views taken along arrows XX and YY in FIG. 1, respectively. Hereinafter, the same or similar parts are denoted by common reference numerals, and redundant description is omitted. However, the drawings are schematic and ratios of dimensions and the like are different from actual ones.

As shown in FIGS. 1 and 2, in the thermal print head 10, a resistor substrate portion 12 </ b> A and a drive circuit substrate portion 12 </ b> B are provided adjacent to each other on the main surface of the heat dissipation substrate 11. In the resistor substrate portion 12 </ _b > A, a support substrate 13 having good heat resistance and thermal conductivity such as Al ₂ O ₃ (alumina) is attached to the main surface of the heat dissipation substrate 11. A thin film-shaped heat insulating layer 14 is arranged in an island shape along the main scanning direction on the support substrate 13. Here, as shown in FIGS. 1 and 3, the separated heat retaining layer 14 extends in the main scanning direction on the support substrate 13 and is integrated with the conventional glaze layer 104. In contrast, the heating elements adjacent to each other are formed so as to be separated from each other. A heating resistor layer 15 is formed so as to cover the surface of the separated heat insulating layer 14 and the surface of the support substrate 13.

  Similar to the description in the prior art, the first electrode 16a and the second electrode 16b, which are overlapped and electrically connected to the heating resistor layer 15, are arranged to face each other with the gap G interposed therebetween. The heating resistor layer 15 exposed in the gap G becomes the heating portion 17. In this way, the heat generating portions 17 of the heat generating elements are formed on the separate heat insulating layers 14 separated from each other. A pair of electrodes 16 including the first electrode 16a and the second electrode 16b and the heat generating portion 17 are used as one heat generating element, and a predetermined number, for example, 2056 heat generating element arrays are arranged in a row in the main scanning direction of the thermal print head. Placed in. Here, one heat generating element has a heat generating portion 17 having a so-called 1-bit configuration. And the edge part of a pair of electrode 16 is exposed for the bonding wire connection mentioned later, and the whole is coat | covered with the protective film 18 with good heat conductivity.

  The drive circuit board portion 12B has a drive circuit board 19 adhered to the heat dissipation board 11, a circuit pattern or the like is formed on the surface of the board, and a drive IC 20 or the like is mounted. The drive IC 20 and the pair of electrodes 16 and the circuit pattern are electrically connected by a bonding wire W, and the bonding wire W and the drive IC 20 are hermetically sealed by a sealing material 21 made of, for example, epoxy resin. .

  In forming an image on a recording medium using the thermal print head 10, the recording medium is sandwiched between a protective film 18 on the heat generating portion 17 area and a so-called platen roller, and at a predetermined speed in the sub-scanning direction. Be transported. Here, the first electrode 16a of the specific heating element is selected and set to the ground potential, and for example, energization is performed with the second electrode 16b of the common electrode applied to several tens of volts. The heat generating part 17 generates heat. In the conveyance, for example, the heat-sensitive recording medium is heated by the heat generating unit 17, and the recording medium is printed by the heat.

  In the thermal print head 10, the heat dissipation substrate 11 is made of, for example, Al (aluminum) metal, and the support substrate 13 is usually a support substrate made of an insulating material having heat resistance, and in addition to alumina ceramics, silicon, quartz And silicon carbide. And this support substrate 13 is affixed on the surface of the thermal radiation board | substrate 11 with resin adhesives, such as a double-sided tape with good heat conductivity, and silicone.

The separated heat retaining layer 14 is an insulating thin film made of an insulating material having an appropriate heat storage and heat dissipation action of the heat generated by the heat generating portion 17 and having surface smoothness. Examples of such a separated heat insulating layer 14 include a SiO ₂ film (silicon oxide film), a SiON film (silicon oxynitride film), and a SiN film (silicon nitride film). Here, these insulating thin films preferably have a thickness of 10 μm or less. With such a film thickness, the heat capacity is reduced, and even in the operation of the thermal print head, the problem of heat storage as in the prior art does not occur and the speeding up is facilitated. Note that a small amount of an additive such as metal fine particles that increase the thermal conductivity may be mixed in the separated heat insulating layer 14.

  The heating resistor layer 15 is made of, for example, a TaSiO, NbSiO, TaSiNO, or TiSiCO based electric resistor material. The pair of electrodes 16 serving as energization electrodes for the first electrode 16a and the second electrode 16b are preferably as low as possible. For example, the main material is a metal such as Al, Cu (copper), or an AlCu alloy. The

The protective film 18 is made of a hard and dense insulating material such as a SiO ₂ film, a SiN film, a SiON film, or a SiC film (silicon carbide film). Here, when at least Si (silicon) and carbon (C) are contained in the outermost surface of the protective film 18, the thermal conductivity is increased, which is preferable. The protective film 18 covers the pair of electrodes 16 and the heat generating portion 17 of the heat generating element array, and protects against wear caused by pressure contact or sliding contact of the recording medium, and corrosion due to contact with moisture contained in the atmosphere. Have. Furthermore, a wear-resistant layer such as a TiN film that also serves as a static elimination can be provided on the surface of the protective layer.

Next, a method for manufacturing the thermal print head 10 will be described. First, an elongated support substrate 13 made of alumina and having a width of about several mm in the sub-scanning direction and a thickness of 0.5 mm to 1 mm is prepared. Then, an insulating thin film such as a SiO ₂ film, a SiON film, or a SiN film having a film thickness of 1 μm to 10 μm, for example, 5 μm is deposited on the surface of the support substrate 13 by a sputtering apparatus, a vacuum evaporation apparatus, a CVD apparatus, or other film forming apparatuses. . Next, the insulating thin film thus formed is processed into an island shape by a photolithographic technique and a selective etching using the etching mask, that is, a photo-engraving process. A separate heat insulating layer 14 is formed. Here, the insulator thin film may be formed in a laminated structure selected from a SiO ₂ film, a SiON film, or a SiN film.

  Here, the selective etching of the insulator thin film is preferably performed by wet etching. By this wet etching, the cross-sectional shape of the end portion of the separated heat insulating layer 14 is tapered. If the end portion of the separated heat insulating layer 14 is tapered, the thin heating resistor layer 15 and the pair of electrodes 16 disposed thereon are prevented from being disconnected, and a high manufacturing yield of the thermal print head 10 is achieved. can get.

  In addition, an insulator thin film deposited by a film forming apparatus such as a sputtering apparatus has a smooth surface and can be controlled to have a thin film thickness unlike a film formed by a screen printing method as in the prior art. . For this reason, fine patterning of the separated heat insulating layer 14 formed using this insulator thin film is facilitated.

Next, a TaSiO ₂ film having a thickness of about 0.08 μm is formed on the surface of the separated heat retaining layer 14 and the surface of the support substrate 13 by, for example, a sputtering method, and then the heating resistor layer 15 is formed by a sputtering method. For example, an electrode film such as an Al film or an AlCu alloy film having a film thickness of about 0.8 μm is formed. Then, the first electrode 16a and the second electrode 16b, which serve as energization electrodes of the heating element array, and the heating resistor layer 15 are patterned by a photolithography process. Further, the electrode film is etched by the photolithography process to form the gap G and the heat generating portion 17 is formed. In this way, the heat generating portions 17 of the respective heat generating elements are formed on the separate heat insulating layers 14 separated from each other.

  Thereafter, a protective film 18 that covers the entire surface is formed by sputtering. Here, the protective film 18 is deposited to a film thickness of, for example, about 5 μm to 10 μm.

  Next, the resistor substrate portion 12A and a drive circuit substrate portion 12B in which, for example, a bare chip drive IC 20 is incorporated in advance are placed and fixed on the heat dissipation substrate 11 made of an aluminum plate or the like via an adhesive. Then, all the energization electrodes of the heating element array are electrically connected to the bonding pads on the output side of the driving IC 20 with bonding wires W made of, for example, Al wires or Au wires. Further, the bonding pad on the input side of the driving IC 20 is electrically connected to the circuit pattern of the driving circuit board 19 by the bonding wire W. Finally, the driving IC 20 and the bonding wire W are hermetically sealed with the sealing material 21 by a known mounting technique. Thus, the thermal print head 10 of this embodiment is completed.

  In this embodiment, the thermal print head 10 is separated in which the heat generating portions 17 of the respective heat generating elements of the high density, for example, element density 20 / mm, 2056 heat generating element arrays arranged in the main scanning direction are separated. The structure is formed on the heat insulating layer 14. With such a structure, in the printing of the heating elements of the heating element array, there is almost no influence of heat storage by the adjacent heating elements. Further, it is not necessary to control the thermal history as described in the prior art, that is, to secure an appropriate non-printing time for guaranteeing the heat dissipation, and it is possible to shorten the non-printing time when printing adjacent heating elements. .

  Moreover, in the thermal print head 10 of this embodiment, since the separated heat insulating layer 14 can be simplified so that the film thickness does not exceed 10 μm, the heat storage capacity thereof is, for example, 1 than that of the conventional glaze layer 104. This is a significant reduction to about / 10. For this reason, the heat generating portion 17 of each heat generating element is heated to a required temperature for printing in a short time. Moreover, rapid heat dissipation of the separated heat insulating layer 14 is facilitated. In this way, it is easy to shorten the printing time in the heating element.

  Since the separated heat retaining layer 14 can sufficiently dissipate heat, the cutout of the print points is improved and the image quality blur in the sub-scanning direction is eliminated. As described above, the thermal print head 10 according to the present embodiment can increase the operation speed and improve the image quality.

  Next, another embodiment of the present invention will be described with reference to FIG. In the thermal print head 10a of this embodiment, in a predetermined number, for example, 2056 heating element arrays arranged in the main scanning direction, the separate heat insulating layers 14 are respectively formed in the heating portions 17a and 17b of the pair of heating elements. The Here, FIG. 4 is a partially cut-out top view of a part of the thermal print head 10a according to another embodiment.

  As shown in FIG. 4, the thermal print head 10a has the same structure as that described in the first embodiment, but one heating element has heating portions 17a and 17b having a so-called 2-bit configuration. Is different from the 1-bit configuration in the first embodiment.

  As shown in FIG. 4, in the thermal print head 10 a, in the resistor substrate portion 12 </ b> A, the support substrate 13 is stuck on the main surface of the heat dissipation substrate 11, and the separated heat insulating layer 14 is the main substrate on the support substrate 13. It is arranged in an island shape along the scanning direction. Here, the separated heat retaining layer 14 is formed so as to be separated between the heating elements having a 2-bit configuration.

  That is, the heating resistor layer 15 is formed by covering the surface of the separated heat insulating layer 14 and the surface of the support substrate 13. In addition, a first electrode 16a, a second electrode 16b, and a third electrode 16c having a folded electrode structure that is layered and electrically connected to the heating resistor layer 15 are arranged as energization electrodes. The heating resistor layer 15 exposed in the gap between the first electrode 16a and the third electrode 16c and the gap between the second electrode 16b and the third electrode 16c constitutes the 2-bit heating portions 17a and 17b. In this manner, the heat generating portions 17a and 17b of one heat generating element having a 2-bit configuration are formed on the separate heat insulating layers 14 separated from each other. Then, a predetermined number of, for example, 2056 heating elements having such a 2-bit configuration are arranged in a row in the main scanning direction of the thermal print head. Other structures are the same as those described in the first embodiment.

  In image formation on a recording medium using the thermal print head 10a, the first electrode 16a of a specific heating element is selected and set to the ground potential, and the second electrode 16b is applied to, for example, several tens of volts. Energization is performed between the pair of electrodes, and the heat generating portions 17a and 17b generate heat. Then, the recording medium is pumped in the same manner as described in the first embodiment, and is heated and printed by the heat generating portions 17a and 17b having the 2-bit configuration.

  In the thermal print head 10a of this embodiment, the operation speed and image quality can be easily improved by the effect of the separate heat insulating layer 14 which is exactly the same as that of the above-described embodiment.

  As another embodiment, the separated heat insulating layer 14 is a predetermined number of, for example, 2056 heating element arrays arranged in the main scanning direction of the thermal print head 10, and the heating portions 17 of one or more heating elements. May be formed on one island-shaped separated heat insulating layer 14. In such an embodiment, the heat history control between the heat generating elements in which the heat generating portions 17 are formed on the different separated heat retaining layers 14 is not necessary, but the heat generating portions 17 are formed in the same separated heat retaining layer 14. Thermal history control between the heating elements is necessary. However, even in this case, the non-printing time for the thermal history control is shortened as compared with the case of the prior art, and the speeding up of the operation of the head and the high image quality are facilitated.

  Although the preferred embodiments of the present invention have been described above, the above-described embodiments do not limit the present invention. Those skilled in the art can make various modifications and changes in specific embodiments without departing from the technical idea and technical scope of the present invention.

  For example, the drive circuit board portion 12B may be formed on the same support substrate 13 as the resistor substrate portion 12A. In the above embodiment, the drive circuit board portion 12B may be arranged at a location different from the thermal print heads 10 and 10a. For example, it may be attached to a control device of a recording device, and for example, the output of the drive IC 20 may be transmitted to the resistor substrate portion 12A through the circuit wiring of the flexible wiring board.

  Further, the support substrate 13 and the drive circuit substrate 19 may be attached to the heat dissipation substrate using different adhesives. This is preferable for preventing breakage due to cracks when the support substrate 13 and the drive circuit substrate 19 have different thermal expansion coefficients.

FIG. 2 is a partially cut-out top view of a part of a thermal print head for explaining an embodiment of the present invention. The expanded cross-sectional view of the XX arrow of FIG. The enlarged cross-sectional view of the YY arrow of FIG. The partially cut-out top view which extracted a part of thermal print head for demonstrating another embodiment of this invention. The partially cut-out top view which extracted a part of thermal print head concerning the prior art. FIG. 6 is an enlarged cross-sectional view taken along the line ZZ in FIG. 5.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10, 10a ... Thermal print head, 11 ... Heat dissipation board, 12A ... Resistor board part, 12B ... Drive circuit board part, 13 ... Support board, 14 ... Separate heat insulation layer, 15 ... Heating resistor layer, 16a ... 1st 16b ... second electrode, 16c ... third electrode, 17, 17a, 17b ... heating portion, 18 ... protective film, 19 ... drive circuit board, 20 ... drive IC, 21 ... sealing material, G ... Gap, W ... Bonding wire

Claims (4)

A support substrate;
A plurality of heat insulating layers made of an insulating material formed in an island shape on the surface of the support substrate;
A heating resistor layer formed on the surface of the support substrate including the heat retaining layer;
A heating element group formed by arranging a plurality of sets of electrodes formed with a gap on the heating resistor layer;
The heating resistor layer exposed in the gap portion of the electrode is used as a heating part of the heating element, and a protective film that covers at least the heating part and is laminated on the heat retaining layer and the support substrate;
Have
The thermal print head according to claim 1, wherein each of the heat generating portions is formed on the separated heat insulating layer.   The thermal print head according to claim 1, wherein a cross-sectional shape of an end portion of the heat retaining layer is tapered.   The thermal print head according to claim 1 or 2, wherein the film thickness of the heat insulating layer does not exceed 10 m. Forming an insulator thin film on one main surface of the support substrate;
Etching the insulator thin film to form a plurality of heat insulating layers separated into islands;
A step of stacking and depositing a heating resistor layer and an electrode film covering the heat retaining layer and the support substrate;
The heat generating resistor layer and the electrode film are processed into a required pattern to form a plurality of heat generating elements each having a heat generating portion, and the heat generating portions of the heat generating elements are formed on the separated heat insulating layer. Forming, and
Forming a protective film that covers at least the heat generating portion and is laminated on the heat retaining layer and the support substrate;
A method for manufacturing a thermal printhead, comprising:

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